returns One of the following error codes: - UPLOAD_ERR_OK (no error) - UPLOAD_ERR_INI_SIZE (the uploaded file exceeds the upload_max_filesize directive in php.ini) - UPLOAD_ERR_FORM_SIZE (the uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form) - UPLOAD_ERR_PARTIAL (the uploaded file was only partially uploaded) - UPLOAD_ERR_NO_FILE (no file was uploaded)